By Tom Herrmann / ADOT Communications

In a little more than a month you’ll be able to drive along the new bridge on Interstate 15 through the scenic Virgin River Gorge in northwest Arizona. We thought you might want to see what you’ll be driving on.

This time-lapse video was shot as crews worked in difficult conditions from November through late February to build a southbound span at Virgin River Bridge No. 6. You can see traffic passing in both directions on the northbound span, which was completed last year. Meanwhile, the slideshow below offers stunning images of this project.

Here’s what it takes: Dozens of steel girders, moved into place by huge cranes. Layer after layer of base to support the roadway. Pouring the bridge deck. Adding the surface and the striping. And something you don’t see: Arizona Department of Public Safety troopers keeping drivers safe on the temporarily divided northbound lanes.

Two years of work is just about to come to an end. For most drivers, the bridge may look like just a simple structure. Watching the video, you can see that building a bridge, especially in an environment like the Virgin River Gorge, is anything but.

Yesterday, we took a look at the US 89 landslide repair project from above. Today, we have another angle to show you…

To really get an idea of the progress being made, you’ll want to pay close attention to a couple of areas on the screen.

First, take a look at the cliffs above the damaged roadway. Notice how the much the formation has changed by the end of the video? That’s because crews are removing material from that area above the slide and trucking it below to build a stabilizing buttress. As we explained in this previous post, crews are utilizing heavy-duty equipment, a fleet of enormous trucks and explosives to get the job done.

A rendering of the repair plan.

You’ll also want to take note of the buttress itself at the base of the slope. Once complete, the buttress will act as a wall-like support structure composed of rock material. In the video above, you can see how it’s coming along. See the graphic at left for good rendering of the overall repair plan.

The one-minute, 22-second video above actually represents about three and a half months of work…

In that time, crews on the US 89 landslide repair project have been busy blasting and moving dirt and rock material. By the end of the project, they’ll have moved about one million cubic yards!

If you’ve been following us for a while, you know that the repair work includes moving the roadway alignment about 60 feet away from the landslide area and stabilizing the new road by constructing a downslope buttress. That buttress is being created with the material that’s being excavated from the landslide area (read more about the repairs in this previous post). ADOT anticipates completion of the US 89 repair and opening the new segment for travel by early summer, 2015.

Check back with us tomorrow, here on the blog. We’ve got another time-lapse video that shows the US 89 landslide repair work from another angle!

Late last month, work to demolish the I-10 bridges over Perryville Road got underway in the west Valley and, as you can see above, things went pretty quickly.

Well, it wasn’t exactly as fast as the video depicts. Instead of 30 seconds, it actually took crews about two days to remove roughly 15,670 tons of material.

To allow for the construction of the new bridges over Perryville Road, I-10 traffic was switched last month to newly constructed detour routes along the paths of the future off- and on-ramps for the interchange.

The $18.8 million I-10/Perryville Road interchange project, which is located west of the future I-10/Loop 303 interchange in Goodyear, is scheduled for completion this fall.

Check out our previous blog posts for a look at some other memorable demos we’ve covered.

Accommodating existing traffic is a key priority when ADOT builds a freeway …

Depending on the project, that can mean working out a construction schedule that takes rush hours into account or hiring extra crews to flag and direct traffic through the site.

But, on the Loop 303 project in the West Valley drivers will notice a new construction bypass that (amazingly) was built in around 43 hours this past weekend. The bypass will be in place for the next 10 months and not only will it allow for a more efficient way to haul dirt, but it’s also going to help drivers avoid the construction zone!

Building the bypass

Crews shut down the intersection at Greenway Road and the Loop 303 at 10 p.m. Friday, Dec. 9.

Roughly 8,000 cubic yards of dirt was hauled in from other parts of the project site to build up the road. That dirt was placed Friday night in eight-inch layers and was compacted until it was the right height for the bypass (see video above!). After that, the road was paved and striped on Saturday.

Prior to the weekend work, crews had built everything they could up until the point where the bypass would cross “live” traffic and require the closure. That required even more dirt – about 40,000 cubic yards.

Crews not only had to build the bypass, but also installed temporary concrete barriers, fencing, sidewalk and a traffic signal.

The traffic signal went in Saturday morning after the power was shut off to the “old” signal. The signal pole’s electric meter and pedestal were set to the new location and power was turned on. ADOT wired the signal Sunday morning and installed a common video detection device that will help with signal timing.

After some finishing touches, the bypass was ready and opened to traffic by about 5:15 Sunday evening – 12 hours ahead of schedule!

Last month, as part of our Building a Freeway series, we told you about the massive underground support substructures that help give bridges strength.

Next up in the series is an important -- but temporary -- structure that’s used as crews build a bridge, tunnel or even a box culvert.

It’s called false work, and it is used to support the structure until the concrete gets its desired strength and the bridge can carry its own weight.

Imagine that you’re building a bridge out of popsicle sticks. Those sticks can’t support their own weight at first, so you might use some blocks to give it some support until your glue dries.

Those blocks are the basic equivalent to false work…

But now what happens when your bridge is complete and it’s time to take the false work out so you have a fully functioning bridge?

With the popsicle-stick scenario, pulling the blocks out might be pretty easy once your glue is dry. But with a large bridge or tunnel, it’s not so simple.

Because the false work is so tightly jammed up against the structure that it has been supporting, taking it down safely requires something called a sand-jack.

A sand-jack is a simple concept, but really is genius when you think about it …

Basically, it is a metal, square “box” (see photo below). It gets lined with plastic (to keep moisture out) and filled with sand. A ¾-inch piece of plywood goes on top of that sand and the false work is built on top.

Because the sand is contained, none of the weight is going to settle -- there’s nowhere for the sand to go.

Now, when it’s time to take the false work down, all crews have to do is unbolt the sand jack “box” and blow the sand out of it. That gives crews a few inches of “wiggle room” to pull out the false work.

To do that safely, they’ll first secure the false work with a forklift. Next they’ll carefully remove the false work structure, except for the “lid” (not a technical term, but the best word to describe this part of the false work).

The “lid” is the top, flat part of the false work over which the deck of the bridge or culvert is built. Just pulling out its support would be dangerous … so crews hold the lid up with the use of hydraulic jacks. The jacks will set on top of the concrete structure with long rods that run through the jack, through the concrete deck, and finally connecting to the false work lid. After the false work legs have been removed, the crews will slowly lower the false work lid to the ground (imagine a mechanic jacking up a car, but in reverse).

When the false work (including the lid) is all out, the bridge, tunnel or box culvert is ready to go! Check out the video above for a look at false work and sand jacks in action. The structure being built is a box culvert that will be used as an equipment pass through during construction of the Loop 303. We'll explain more about that one soon. Stay tuned...